Cutting fluids are used in many metal-cutting operations, as well as in grinding, to maintain optimum production rates, minimize tool wear, improve surface finish, etc. One of the primary types of cutting fluids comprise emulsified oils. Emulsified oils form mixtures ranging from emulsions to solutions when mixed with water which, due to their high specific heat, high thermal conductivity, and high heat of vaporization, are one of the most effective cooling media known. Blended with water, usually in the ratio of 1 part oil to 15-20 parts water for cutting, and 40 to 60 parts water for grinding, the water miscible fluids provide excellent cooling and lubrication for metal cutting at high speeds and light pressures.
Usually, a metal forming machine is equipped with its own reservoir of cutting fluid, from which the cutting fluid is drawn for discharge into the cutting area. The cutting fluid is recirculated back to the reservior for reuse. A substantial quantity of the cutting fluid, however, is lost during operation as a result of evaporation and as metal chips are removed. The reservoir, therefore, must be refilled on a frequent basis. When a plant must supply cutting fluid for a large number of metal forming machinings, it becomes imperative that a sufficiently high volumetric flow rate apparatus be provided for supplying cutting fluid to the reservoirs.
As alluded to above, it is also imperative that a proper ratio of oil and water be blended. The precise ratio is determined by carefully considering such factors as the type of machining operation being preformed, the speed at which material is removed, the type of material being machined, etc. An unfavorable or excessive change from the optimum oil/water ratio can possibly result in catastrophic damage to the workpart and/or tool.
Therefore, relating to cutting fluids in general, it is important that a precise ratio between the oil and the water be provided on a continuous basis, and also that a continuous high volumetric flow of the cutting fluid be made available for the metal forming machines.
Examples of the prior art apparatus for transferring liquids may be had in the U.S. Pat. Nos. 3,810,720 to Lartigue et al, issued May 14, 1974, and 3,174,649 to Richardson, issued Mar. 23, 1965. These references disclose apparatus for withdrawing from different vessels predetermined amounts of different liquid media and then combining the media into a single vessel. The apparatuses disclosed in these references, however, are not capable of delivering a continuous flow of measured liquid components to the receptacle as a loss of flow to the receptacle occurs while the respective apparatuses perform the step of measuring the select liquids.